Pockets are features that must be closed. This means that the cross-section of the feature must form a loop.
Pockets can be recognized using one of four methods.
Pockets with bottoms and walls all around can be automatically recognized from solid models. This is the only method that can recognize islands and bottom radaii.
Recognition from selected bottom surfaces
Recognition from selected side surfaces
By extracting feature geometry and chaining curves. This is the only method that can be used to recognize drafted pockets
See also Pocket feature and and Feature recognition surface requirements